To play devil's advocate, you make very good points except when you said:
"There is no quantifiable victor in figure skating - it's not a question of who skates longer, or faster, or jumps higher, or farther, or more often. Figure skating is based entirely on subjective opinions - who a third party feels, in their opinion, is the "winner"."
Because that is exactly what figure skating is, who jumps higher, farther and how often. That is one of the components. Granted, someone else judges and picks the winner, and granted that this method is flawed at times, but are you saying that it is a sport if there is a quantifiable winner?
So then by your definition, boxing isn't a sport, or true wrestling? I mean, often times, there is somebody who "subjectively" picks a winner, much like in skating.
I am interested to hear what your definition of a sport is.
Brian